2. Visualisation of DESeq2 results
1 Preparation
Libraries/utils:
if (!require("librarian")) install.packages("librarian")
librarian::shelf(
# tidyverse
tibble, stringr, tidyr, purrr, dplyr,
# data other
reshape2, santoku, calibrate, readxl, writexl,
DESeq2, DescTools, matrixStats,
# graphics
ggplot2, ggthemes, ggtext, ggrepel, ggpubr,
eulerr, RColorBrewer, cetcolor,
# convenience
here)
if(!exists("ggmaplot2", mode="function")) source("utils.R")Set working directory:
if (Sys.getenv("RSTUDIO")==1) {
# setwd to where the editor is, if the IDE is RStudio
setwd( dirname(rstudioapi::getSourceEditorContext(id = NULL)$path) )
} else {
# setwd to where the editor is in a general way - maybe less failsafe than the previous
setwd(here::here())
# the following checks that the latter went well, but assuming
# that the user has not changed the name of the repo
d <- str_split(getwd(),'/')[[1]][length(str_split(getwd(),'/')[[1]])]
if (d != 'RNAseq-EmcDaSc-adult_midgut') { stop(
paste0("Could not set working directory automatically to where this",
" script resides.\nPlease do `setwd()` manually"))
}
}To save images outside the repo (to reduce size):
figdir <- paste0(c(head(str_split(getwd(),'/')[[1]],-1),
paste0(tail(str_split(getwd(),'/')[[1]],1), '_figures')),
collapse='/')
dir.create(figdir, showWarnings = FALSE)2 RNAseq results visualisation: Principal Components Analysis
2.1 Load and check expression data
We have seen how batch correction is necessary to show a meaningful PCA. Of the different expression measures, vst-normalised data is the most reasonable to make comparisons across samples.
targets <- readRDS('output/targets.RDS')
vsd <- readRDS('output/vst_pseudocounts_batchCorrected.RDS')When performing PCA on RNAseq data, it is often useful to filter genes with very low variance across experimental conditions. To test whether this makes sense in our case:
# get per-gene variance and mean expression
var_vsd <- rowVars(assay(vsd), rm.na=TRUE)
avg_vsd <- rowMeans(assay(vsd))
df <- data.frame(Variance=var_vsd, Mean=avg_vsd)
# plot close to variance==0 with inset:
p1 <- ggplot(df, aes(x=Variance, y=Mean)) +
geom_point(size=0.1, alpha=0.5, colour='#fe4b03') +
geom_vline(xintercept=0, colour='black', size=0.1)
p2 <- ggplot(df, aes(x=Variance, y=Mean)) +
geom_point(alpha=0.1) + xlim(0,0.1) + ylim(5,20) +
theme(panel.background = element_rect(fill='grey90')) +
geom_vline(xintercept=0, colour='#02ccfe')
p1 + annotation_custom(ggplotGrob(p2),
xmin=5, xmax=12,
ymin=5, ymax=25)
Some genes have very low variance (which is the whole point of the
vst transformation), but none of them are zero. There seems
to be little point in drawing an arbitrary threshold, so I move on with
the whole dataset.
2.2 PCA plot
pca <- prcomp(t(assay(vsd)), center=TRUE)
scores <- data.frame(targets$sampleIDs, pca$x[,1:2])
xtitle <- paste0('**PC1** (', round(summary(pca)$importance['Proportion of Variance','PC1']*100,1), ' %)')
ytitle <- paste0('**PC2** (', round(summary(pca)$importance['Proportion of Variance','PC2']*100,1), ' %)')
ptitle <- 'Principal component scores'
stitle <- '(*vst* pseudocounts, batch-corrected)'
ggplot(scores,
aes(x = PC1, y = PC2,
label=factor(targets$sampleIDs),
colour=factor(targets$condition_md) )
) +
# data
geom_vline(xintercept=0, linetype='dashed', colour='grey60', linewidth=0.5) +
geom_hline(yintercept=0, linetype='dashed', colour='grey60', linewidth=0.5) +
geom_point(size=4) +
geom_point(size=2, colour='white', alpha=0.5) +
geom_text_repel(size=4, alpha=0.75,
max.overlaps=Inf,
seed=42,
force=0.3, force_pull=1,
box.padding=1, point.padding=0.5) +
lims(x= c(-100, 150), y = c(-80, 80)) +
# decorations
theme_minimal(base_size=16) +
labs(x=xtitle,
y=ytitle,
title=ptitle,
subtitle=stitle) +
scale_colour_discrete(name="condition") +
theme(legend.text = element_markdown(size=10),
axis.title.x = element_markdown(),
axis.title.y = element_markdown(),
plot.title = element_text(hjust=0.5),
plot.subtitle = element_markdown(hjust=0.5, color="grey40"),
axis.text.x = element_text(color="grey60"),
axis.text.y = element_text(color="grey60"),
axis.ticks.x = element_line(linewidth=0.5, linetype = "solid", color="grey60"),
axis.ticks.y = element_line(linewidth=0.5, linetype = "solid", color="grey60"),
axis.ticks.length=unit(-0.25, "cm"),
panel.border = element_rect(linewidth=1, linetype = "solid", fill = NA),
panel.grid = element_blank())
ggsave('PCA_vsd_batchcorr.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300)3 RNAseq results visualisation: Euler diagrams
To visualise the degree of overlap and independence of the differentially expressed gene sets, I tried both Venn diagrams and UpSet plots in different colourmaps and spatial organisations. Having four genetic conditions made them all too complicated to grasp any pattern at a glance, so I turned to Euler diagrams. These have the advantage of capturing the size of sets and their intersections in the area of the circles and their overlaps, but the disadvantage of doing so only approximately. However, this is a very minor problem that does not affect the message.
3.1 Prepare data
# experimental design and labels
targets <- readRDS('output/targets.RDS')
# DEG data
DaDaOE_deg <- readRDS('output/Control_vs_DaDaOE.RDS')
DaKD_deg <- readRDS('output/Control_vs_DaKD.RDS')
DaOE_deg <- readRDS('output/Control_vs_DaOE.RDS')
ScOE_deg <- readRDS('output/Control_vs_ScOE.RDS')
# gene symbols
dlist <- read.table(file="resources/gene_symbols.txt", header=TRUE)
names(dlist)[[1]] <- 'ensembl_gene_id'
rownames(dlist) <- dlist$ensembl_gene_idNow, for each condition, we will need to get the lists of misregulated genes for a given threshold of fold change:
list_of_degs <- list(DaKD_deg, DaOE_deg, DaDaOE_deg, ScOE_deg)
names_degs <- list('daRNAi', 'da', 'da:da', 'scute')
fc_thresh <- 1.5
regs <- extract_regulated_sets(list_of_degs, names_degs, fc_thresh=fc_thresh)
# attach the results to the DEG data frame for each condition, to be used later
DaKD_deg$reg <- regs$daRNAi
DaOE_deg$reg <- regs$da
DaDaOE_deg$reg <- regs$`da:da`
ScOE_deg$reg <- regs$scute
regs[500:504,]Now we need to turn this into logicals:
upreg <- get_deg_logical(regs,'up')
downreg <- get_deg_logical(regs,'down')3.2 Plot diagrams
Using instructions from the vignette:
up_colours <- c(
brewer.pal(9,'BrBG')[3], # daRNAi brown
brewer.pal(9,'YlOrBr')[4], # daOVEX yellow/orange
brewer.pal(9,'Reds')[5], # dadaOVEX red
brewer.pal(9,'PuRd')[3] # scOVEX violet
)
down_colours <- c(
brewer.pal(11,'PRGn')[8], # daRNAi green
brewer.pal(11,'RdYlBu')[8], # daOVEX pale blue
brewer.pal(11,'RdBu')[9], # dadaOVEX blue
brewer.pal(9,'Purples')[5] # scOVEX purple
)
upfit <- euler(upreg, loss = 'region', loss_aggregator = 'max')
downfit <- euler(downreg, loss = 'region', loss_aggregator = 'max')
upplot <- plot(upfit,
fill = up_colours,
quantities = TRUE)
downplot <- plot(downfit,
fill = down_colours,
quantities = TRUE)
# save it
pdf(file=paste0(figdir,'/euler_up.pdf'),
width=10, height=12)
upplot
dev.off()
pdf(file=paste0(figdir,'/euler_down.pdf'),
width=10, height=12)
downplot
dev.off()
print(upplot)
print(downplot)
4 RNAseq results visualisation: MA plots
We use M (log ratio) and A (mean average) plots to have an overview of the distribution of differential gene expression data. Alongside this, it would be informative to visualise where some individual marker genes lie within the distribution, so we describe next how the list of marker genes was selected.
4.1 List of marker genes
The aim is to have a list of genes that could serve as cell type exclusive markers. We will only consider a simplified cell type classification: ISC, EB, EE, EC of the adult posterior midgut. They must be either expressed exclusively in a cell type (e.g. Delta), or functionally promote one cell type only (e.g. phyllopod). We start with a curated list and the markers defined by the Fly Cell Atlas consortium. Then we will remove redundancy.
- Curated markers:
genes_of_interest <- read_excel('resources/genes_of_interest.xlsx', sheet='gene_table') %>%
dplyr::select(gene_symbol, bonafide_celltype) %>%
filter(bonafide_celltype != 'NA') %>%
dplyr::rename(celltype = bonafide_celltype) %>%
group_by(celltype) %>%
dplyr::summarise(gene_symbol=paste(gene_symbol, collapse=', '))
genes_of_interest- FCA markers:
markers <- read_xlsx(file.path(getwd(), 'resources', 'science.abk2432_table s2.xlsx')) %>%
# get only the gut epithelium/muscle cell types
filter(Tissue=='gut' | `Annotation...1`=='enteroendocrine cell') %>%
# remove a hybrid/transitional cell type
filter(!str_detect(`Annotation...1`, 'differentiating')) %>%
# remove muscle/artefact cells
filter(!str_detect(`Broad annotation`, 'muscle|artefact')) %>%
# get just the columns with marker names
dplyr::select(contains(c('Annotation...1', 'Marker'))) %>%
# join all markers in a new column
unite(gene_symbol, contains('Markers'), sep = ', ')
names(markers)[[1]] <- 'celltype'
markers- Merge markers:
# some markers are spelled differently in the Fly Cell Atlas and our genome annotation:
missd.spelld <- c(`wntD, `='', `LManIV, `='', `CG31269, `='', `CG43208, `='', `orcokinin B, `='',
AstB='Mip', poxn='Poxn')
markers <- rbind(genes_of_interest, markers) %>%
# merge same cell type markers
group_by(celltype) %>%
dplyr::summarise(gene_symbol=paste(gene_symbol, collapse=', ')) %>%
# correct difference in synonym/capitalisation with DEG data...
# ... while all gene symbols are in one string
dplyr::mutate(gene_symbol = str_replace_all(gene_symbol, missd.spelld)) %>%
# make each gene name an independent string
rowwise() %>% dplyr::mutate(markers = list(unique(str_split(gene_symbol, ', ')[[1]])))
markers- Filter non-cell type-exclusive markers
# filter by exclusivity, but keeping what is common to all enterocytes
## first identify all EC markers
ECmarkers <- markers %>%
filter(str_detect(celltype, 'enterocyte')) %>%
dplyr::select(markers) %>%
unlist(use.names = FALSE) %>%
unique() %>% as.list()
## then non-EC cell markers, with all their repetitions!!
nonECmarkers <- markers %>%
filter(!str_detect(celltype, 'enterocyte')) %>%
dplyr::select(markers) %>%
unlist(use.names = FALSE) %>% as.list()
## get all markers with one occurrence (≠unique!)
repmarkers <- unlist(c(ECmarkers, nonECmarkers))
reps <- rle(sort(repmarkers))
xmarkers <- reps$values[reps$lengths==1]
## apply criterion of exclusivity
exclude <- function(x) x[x %in% xmarkers]
markers <- markers %>%
dplyr::mutate(exclusive = list(exclude(markers)))
pmgcelltypes <- c('intestinal stem cell', 'enteroblast', 'enteroendocrine cell', 'enterocyte of posterior adult midgut epithelium')
pmg.markers <- markers %>%
filter(celltype %in% pmgcelltypes) %>%
dplyr::select(c(1,4)) %>%
dplyr::rename(xmarkers = exclusive)
pmg.markers- Add cell type colours HEX codes
write_xlsx(unnest_longer(pmg.markers, xmarkers) %>%
dplyr::rename(gene_symbol = xmarkers),
path = 'output/preliminary_Table S4.xlsx')
cellcolours <- c('EB'='#56B2E9', 'EC'='#009E73', 'EE'='#CC79A7', 'ISC'='#D55E00')
pmg.markers$cellcolour <- cellcolours4.2 MA plots using ggpubr::ggmaplot wrappers
MA plot for daughterless knockdown
repulsion <- list(box.padding = 0.1,
point.padding = 0.8,
nudge_x = 3,
nudge_y = 2,
force = 1,
force_pull = 0,
seed.up = 42,
seed.dn = 50,
xlims.up = c(14, NA),
ylims.up = c(5, NA),
xlims.dn = c(18, NA),
ylims.dn = c(NA, -1))
ggmaplot2(deg = DaKD_deg,
fc_thresh = fc_thresh,
markers = pmg.markers,
md_label = '*esg > da^RNAi^*',
repulsion = repulsion)
Now with cell type-specific colours:
repulsion <- list(box.padding = 0.08,
point.padding = 0.1,
nudge_x = 0,
nudge_y = 0,
force = 1,
force_pull = -0.004,
seed.up = 42,
seed.dn = 5,
xlims.up = c(12, NA),
ylims.up = c(5.5, NA),
xlims.dn = c(16, NA),
ylims.dn = c(NA, -1))
ggmaplot3(deg = DaKD_deg,
fc_thresh = fc_thresh,
markers = pmg.markers,
md_label = '*esg > da^RNAi^*',
repulsion = repulsion)
suppressMessages(ggsave('MA_daKD.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300))MA plot for daughterless overexpression
repulsion <- list(box.padding = 0.1,
point.padding = 0.1,
force = 1.5,
force_pull = -0.003,
nudge_x.up = 0,
nudge_y.up = 0,
nudge_x.dn = 0,
nudge_y.dn = 0,
seed.up = 42,
seed.dn = 5,
xlims.up = c(12, NA),
ylims.up = c(5, NA),
xlims.dn = c(16, NA),
ylims.dn = c(NA, -1))
ggmaplot3(deg = DaOE_deg,
fc_thresh = fc_thresh,
markers = pmg.markers,
md_label = '*esg > da*',
repulsion = repulsion)
suppressMessages(ggsave('MA_daOE.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300))MA plot for the overexpression of the Daughterless homodimer
repulsion <- list(box.padding = 0.01,
point.padding = 0.1,
nudge_x = 0,
nudge_y = 0,
force = 1,
force_pull = -0.004,
seed.up = 42,
seed.dn = 5,
xlims.up = c(16, NA),
ylims.up = c(3, NA),
xlims.dn = c(16, NA),
ylims.dn = c(NA, -2))
ggmaplot3(deg = DaDaOE_deg,
fc_thresh = fc_thresh,
markers = pmg.markers,
md_label = '*esg > da:da*',
repulsion = repulsion)
suppressMessages(ggsave('MA_dadaOE.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300))MA plot for the scute overexpression
repulsion <- list(box.padding = 0.01,
point.padding = 0.1,
nudge_x = 0,
nudge_y = 0,
force = 0.7,
force_pull = -0.003,
seed.up = 42,
seed.dn = 5,
xlims.up = c(8, NA),
ylims.up = c(7, NA),
xlims.dn = c(8, NA),
ylims.dn = c(NA, -6))
ggmaplot3(deg = ScOE_deg,
fc_thresh = 2,
markers = pmg.markers,
md_label = '*esg > scute*',
repulsion = repulsion)
suppressMessages(ggsave('MA_ScOE.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300))5 Heatmaps of individual genes
It is useful to have a representation of the magnitude of the
expression changes across samples of a group of genes. Heatmaps seem the
best option, provided there is also a representation of whether the
changes are statistically significant. To do this, I use a wrapper of
pretty heatmap package main function, pheatmap, to
draw significance-coloured asterisks as a 2nd layer of information.
5.1 Heatmap of cell type-exclusive markers
# get genes of interest (cell type exclusive markers, in this case) in tidy form
tidy.markers <- pmg.markers %>% unnest_longer(xmarkers) %>%
dplyr::rename(gene_symbol = xmarkers)
# add markdown description of genotype
DaKD_deg$condition <- '*da^RNAi^*'
DaOE_deg$condition <- '*da*'
DaDaOE_deg$condition <- '*da:da*'
ScOE_deg$condition <- '*scute*'
# get all the information needed in a df
genehm.df <- bind_rows(ScOE_deg, DaDaOE_deg, DaOE_deg, DaKD_deg) %>%
dplyr::select(ensemblGeneID, gene_symbol, log2FoldChange, padj, condition) %>%
dplyr::rename(p.adjust = padj) %>%
filter(gene_symbol %in% tidy.markers$gene_symbol) %>%
merge(., tidy.markers, by = 'gene_symbol') %>%
dplyr::mutate(condition = factor(condition, levels=c("*scute*", "*da:da*", "*da*", "*da^RNAi^*")))
# pass df to pheatmap wrapper
p <- layer.heatmaph(genehm.df, arr='celltype')
p + geom_hline(aes(yintercept=3.5), linewidth = 0.5) +
theme(plot.margin = margin(r = 25))
This arrangement is more informative:
p <- layer.heatmapv(genehm.df, cluster=TRUE)
p + geom_vline(aes(xintercept=3.5), linewidth = 0.5)
suppressMessages(ggsave('marker_heatmap.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300))5.1 Heatmap of the Enhancer of split-Complex genes
# prepare data
Espl.df <- bind_rows(ScOE_deg, DaDaOE_deg, DaOE_deg, DaKD_deg) %>%
dplyr::select(ensemblGeneID, gene_symbol, log2FoldChange, padj, condition) %>%
dplyr::rename(p.adjust = padj) %>%
filter(grepl("^E\\(spl\\)", gene_symbol)) %>%
dplyr::mutate(condition = factor(condition, levels=c("*scute*", "*da:da*", "*da*", "*da^RNAi^*"))) %>%
dplyr::mutate(cellcolour = "#000000")
# plot
p <- layer.heatmapv(Espl.df, cluster=TRUE)
p + geom_vline(aes(xintercept=3.5), linewidth = 0.5)
suppressMessages(ggsave('Esplit_heatmap.pdf', plot = last_plot(), device = 'pdf',
path = figdir, dpi = 300))